Need help, R3 vs Hemi, 6.1/6.4,,turbos??

Want to start gathering cash for parts for a future build. Currently have a 68 fastback barracuda with a 340, 340 has a very mild cam just a touch above stock, LD340 intake and a afb 1406 carb, exhaust manifolds are TA hi-po manifolds. Question is for what I want to achieve whats the best route to go, most efficient and cost effective. In the end I want to be able to compete with hellcats on the street and at the strip, how would you go about a build like this? I like the idea of turbos and I hear the newer hemi’s would be better but I like my 4 speed trans and also the idea of an older engine taking on a newer one and winning. Thoughts? Losing the 4 speed isn’t a deal breaker, just want a car that is streetable and also able to compete and show some hellcats the taillights on my 68 barracuda